Method of manufacturing dielectric ceramic compositions of lead-based perovskite

ABSTRACT

A manufacturing method for dielectric ceramic compositions of lead-based perovskite containing lead magnesium tungstate [Pb(Mg 1/2  W 1/2 )O 3  ] as a component which is characterized in that magnesium tungstate powder [MgWO 4  ] is used as a starting material instead of MgO and WO 3  powder.

BACKGROUND OF THE INVENTION

This invention relates to a method for manufacturing dielectric ceramic compositions of high dielectric constant, and more particularly to a manufacturing method of the material for capacitors especially suitable for multilayer ceramic capacitors.

Along with the trend of miniaturization, electronic components are being made in chip-type structure. Requirements for multilayer ceramic chip capacitors, in particular, have become more stringent in reliability, compactness, large capacity, low cost, and small temperature dependency of capacitance and high insulating resistance. In the prior art, such requirements were met by mainly using ceramics of barium titanate (BaTiO₃) group and shifting the Curie point by adding an additive or substituting the composition, in part, so as to lower the temperature dependency. Recently, attention has been focused on dielectrics having a composition of lead-based perovskite structure and par containing lead magnesium tungstate [Pb(Mg_(1/2) W_(1/2))O₃ ] as disclosed in U.S. Pat. No. 4,450,240 granted on May 22, 1984 for Haruhiko Miyamoto et. al.

Barium titanate (BaTiO₃) group is excellent in temperature characteristics, but its dielectric constant is approximately 3000 at maximum which cannot satisfy the stringent requirements for small multilayer ceramic chip capacitors. The perovskite structure compound mainly comprising lead magnesium tungstate [Pb(Mg_(1/2) W_(1/2))O₃ ] is antiferroelectric at a temperature below the phase transition temperature (Curie temperature), and as a solid solution, is high in dielectric constant and insulating resistance and small in temperature variation.

However, following problems arise if the conventional method of synthesizing lead magnesium tungstate [Pb(Mg_(1/2) W_(1/2))O₃ ] is attempted in which powders of lead oxide (PbO), magnesium oxide (MgO), and tungsten oxide are respectively mixed, calcined, pulverized and sintered. In this group, the reaction of lead oxide and tungsten oxide takes place preferentially at relatively low temperatures to produce Pb₂ WO₅ and compounds of unfixed ratios. These compounds are in a liquid phase at temperatures of 750°˜850° C. which is the conventional range of calcination, and tend to agglutinate at the time of calcination to prevent formation of a uniform composition. Magnesium oxide is relatively stable in this group, reacts weakly, and often remains in the sintered final product. As the liquid phase takes place, if calcination temperature is elevated to promote magnesium oxide reaction, powders become agglutinated and caked simultaneously. Similar problems are encountered in the case of perovskite solid solution containing as a component, lead magnesium tungstate. More specifically, when it is used in the manufacture of multilayer ceramic capacitors, the magnesium oxide reaction is not entirely complete, leaving unreacted residue within the sintered product after the sintering process. At the same time, excess lead oxide and tungsten oxide form a liquid phase an agglutinate at the grain boundary or at the triple point. Therefore, the dielectric constant of the sintered products becomes low, the temperature characteristics of the dielectric constant extremely unstable, and the resistivity and breakdown voltage reduced.

SUMMARY OF THE INVENTION

An object of this invention is to provide a method for stable manufacture of dielectric ceramic compositions having a high dielectric constant, a stable temperature variation ratio, a high insulating resistance, and a high breakdown voltage, when a perovskite solid solution containing lead magnesium tungstate [Pb(Mg_(1/2) W_(1/2))O₃ ] is used as a component.

According to this invention manufacturing method of dielectric ceramic compositions, the manufacturing method of a perovskite structure composition comprising as a component lead magnesium tungstate [Pb(Mg_(1/2) W_(1/2))O₃ ] is characterized by the use of magnesium tungstate compound (MgWO₄) powder instead of the powders of MgO and WO₃, conventional starting raw materials.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of this invention will now be explained more specifically by referring to Tables 1 through 3.

The magnesium tungstate (MgWO₄) powder is synthesized first according to a so-called mixed oxide method. Tungsten oxide and magnesium oxide powders were weighed to the mole ratio of 1:1, and wet mixed with a ball mill. Tungsten oxide (WO₃) and magnesium oxide (MgO) of more than 99.9% purity were used as the material. The mixture was filtrated, dried and reacted at 750˜1000° C. to obtain magnesium tungstate (MgWO₄) powder.

Powders of lead oxide (PbO), nickel oxide (NiO), niobium oxide (Nb₂ O₅), magnesium oxide (MgO), titanium oxide (TiO₂), and magnesium tungstate (MgWO₄) of more than 99% purity were used respectively as starting materials and weighed to the mix ratios shown in the tables. Weighed materials were wet mixed with a ball mill, filtrated, dried, and calcined at 750°˜850° C. The powders were wet pulverized, filtrated, dried, mixed with 5% polyvinyl alcohol aqueous solution as a binder, granulated, and pressed to mold 16 discs of 16 mm diameter and 2 mm thickness for each of the mix ratios. These discs were sintered in the air at 925°˜1050° C. for one hour. Silver electrodes were bonded by baking on both surfaces of the sintered disc samples at 600° C., and the capacity and dielectric loss were measured using a digital LCR meter at 1 kHz, 1 Vrms and -55°˜125° C. Based on the above, dielectric constant and changes thereof at various temperatures were calculated. By applying 50 V for one second, insulation resistance at 20° C. was measured by means of a ultra high insulating meter, and specific resistivity was calculated. Characteristic values corresponding to each mix ratio (composition) were obtained from the means of characteristic values for each of the four samples.

Tables 1 through 3 show the relation of the mix ratios against the dielectric constant, dielectric loss and specific resistivity of thus obtained ceramic composition. For comparison, powders obtained by the prior art method wherein lead oxide (PbO), magnesium oxide (MgO), tungsten oxide (WO₃), nickel oxide (NiO), niobium oxide (Nb₂ O₅), and titanium oxide (TiO₂) of more than 99% purity were weighed and mixed simultaneously to above, calcined at 750°˜850° C., and wet pulverized with a ball mill. The resulting powders were molded, sintered and formed as sintered products in the form of disc. The conditions for calcination, wet-pulverization, press-molding, sintering, and processes therefor were similar to those used for at various temperature. Tables 1 through 3 show the relation of the dielectric constant, dielectric loss, and specific resistance of thus produced discs and mix ratios of the ceramic composition for the purpose of comparison. (The samples marked with * in Table 1).

The obtained powders were processed into multilayer ceramic capacitors by the following method and destroyed to measure the breakdown voltage.

Each of the ceramic composition powders was mixed with an organic binder and an organic solvent to produce a slurry mixture. The slurry was cast, dried on a polyester film of 30 μm thickness by the doctor blade method and cut into predetermined shapes to obtain green sheets. The green sheets were printed with the inner electrode patterns by the screen printing method and dried. A silver palladium paste was used as the paste for inner electrodes. As protecting layers, five unprinted green sheets were laminated on each side, and 10 printed sheets were laminated therebetween in the predetermined direction. Thus, the total of 20 sheets were thermally pressed for integration. The laminated sheets were cut into predetermined shapes and then sintered at the temperature of 900°˜1050° C. after removing the organic binder by pyrolysis. Exterior electrodes were formed by applying a silver paste and firing to produce multilayer ceramic capacitors. Breakdown voltage was obtained by calculating mean values for each of 10 capacitors which were applied with D.C. voltages. The result is shown in Tables 1 through 3.

                                      TABLE 1                                      __________________________________________________________________________     Ratio of main components          sintering                                    Pb(Mg 1/2   Pb(Ni 1/3     materials                                                                              temperature                                  No. W 1/2)O.sub.3                                                                          Nb 2/3)O.sub.3                                                                        PbTiO.sub.3                                                                           used    (°C.)                                 __________________________________________________________________________     1*  0.55    0      0.45   PbO      975                                         2*  0.55    0      0.45   MgO     1000                                         3*  0.55    0      0.45   WO.sub.3                                                                               1025                                         4*  0.55    0      0.45   TiO.sub.2                                                                              1050                                         5   0.55    0      0.45   PbO      975                                         6   0.55    0      0.45   MgWO.sub.4                                                                             1000                                         7   0.55    0      0.45   TiO.sub.2                                                                              1025                                         8   0.55    0      0.45           1050                                         9*  0.98    0      0.02   PbO      925                                         10* 0.98    0      0.02   MgO      950                                         11* 0.98    0      0.02   WO.sub.3                                                                                975                                         12* 0.98    0      0.02   TiO.sub.2                                                                              1000                                         13  0.98    0      0.02   PbO      925                                         14  0.98    0      0.02   MgWO.sub.4                                                                              950                                         15  0.98    0      0.02   TiO.sub.2                                                                               975                                         16  0.98    0      0.02           1000                                         __________________________________________________________________________                     temperature        breakdown                                                   with the           voltage of                                                  maximum maximum                                                                             resistivity                                                                          laminated                                   dielectric constant                                                                            dielectric                                                                             dielectric                                                                          (20° C.                                                                       ceramic                                     No.                                                                               -55° C.                                                                      20° C.                                                                      125° C.                                                                     constant (°C.)                                                                  constant                                                                            n · cm)                                                                     capacitor (V)                               __________________________________________________________________________     1* 1010 1480                                                                               1070                                                                               35      1560 9.6 × 10.sup.12                                                                100                                         2* 1630 2330                                                                               1640                                                                               19      2340 1.0 × 10.sup.13                                                                130                                         3* 2520 3190                                                                               2180                                                                                5      3360 1.2 × 10.sup.13                                                                150                                         4* 3180 3580                                                                               2390                                                                               -8      3980 1.3 × 10.sup.13                                                                180                                         5  2780 3390                                                                               2210                                                                               -3      3690 1.2 × 10.sup.13                                                                350                                         6  3200 3610                                                                               2410                                                                               -6      4010 1.3 × 10.sup.13                                                                510                                         7  3420 3850                                                                               2560                                                                               -7      4280 1.3 × 10.sup.13                                                                490                                         8  3450 3890                                                                               2590                                                                               -8      4320 1.4 × 10.sup.13                                                                550                                         9*  170  350                                                                                390                                                                               26       530 1.2 × 10.sup.13                                                                 80                                         10*                                                                                190  540                                                                                420                                                                               23       560 1.4 × 10.sup.13                                                                 70                                         11*                                                                                200  600                                                                                440                                                                               20       600 1.7 × 10.sup.13                                                                110                                         12*                                                                                220  640                                                                                460                                                                               17       650 2.1 × 10.sup.13                                                                 90                                         13  260  780                                                                                600                                                                               21       800 2.2 × 10.sup.13                                                                380                                         14  270  810                                                                                620                                                                               19       820 2.3 × 10.sup.13                                                                430                                         15  280  830                                                                                630                                                                               18       840 2.3 × 10.sup.13                                                                410                                         16  280  830                                                                                630                                                                               17       850 2.4 × 10.sup.13                                                                420                                         __________________________________________________________________________      Note                                                                           Those marked with * are not included in the scope of this invention.     

                                      TABLE 2                                      __________________________________________________________________________     Ratio of main components          sintering                                    Pb(Mg 1/2   Pb(Ni 1/3     materials                                                                              temperature                                  No. W 1/2)O.sub.3                                                                          Nb 2/3)O.sub.3                                                                        PbTiO.sub.3                                                                           used    (°C.)                                 __________________________________________________________________________     17* 0.30    0.30   0.40   PbO      975                                         18* 0.30    0.30   0.40   MgO     1000                                         19* 0.30    0.30   0.40   WO.sub.3                                                                               1025                                         20* 0.30    0.30   0.40   NiO     1050                                                                   Nb.sub.2 O.sub.5                                                               TiO.sub.2                                            21  0.30    0.30   0.40   PbO      975                                         22  0.30    0.30   0.40   MgWO.sub.4                                                                             1000                                         23  0.30    0.30   0.40   NiO     1025                                         24  0.30    0.30   0.40   Nb.sub.2 O.sub.5                                                                       1050                                                                   TiO.sub.2                                            25  0.30    0.30   0.40   PbO      975                                         26  0.30    0.30   0.40   MgWO.sub.4                                                                             1000                                         27  0.30    0.30   0.40   NiNb.sub.2 O.sub.6                                                                     1025                                         28  0.30    0.30   0.40   TiO.sub.2                                                                              1050                                         29* 0.30    0.30   0.40   PbO      975                                         30* 0.30    0.30   0.40   MgO     1000                                         31* 0.30    0.30   0.40   WO.sub.3                                                                               1025                                         32* 0.30    0.30   0.40   NiNb.sub.2 O.sub.6                                                                     1050                                                                   TiO.sub.2                                            __________________________________________________________________________                     temperature        breakdown                                                   with the           voltage of                                                  maximum maximum                                                                             resistivity                                                                          laminated                                   dielectric constant                                                                            dielectric                                                                             dielectric                                                                          (20° C.                                                                       ceramic                                     No.                                                                               -55° C.                                                                      20° C.                                                                      125° C.                                                                     constant (°C.)                                                                  constant                                                                            n · cm)                                                                     capacitor (V)                               __________________________________________________________________________     17*                                                                               4010  6830                                                                              5720                                                                               40       7780                                                                               2.5 × 10.sup.12                                                                180                                         18*                                                                               4600 10190                                                                              4110                                                                               20      10210                                                                               2.9 × 10.sup.12                                                                280                                         19*                                                                               4910 10380                                                                              4170                                                                               23      10460                                                                               3.8 × 10.sup.12                                                                250                                         20*                                                                               5190 10960                                                                              4250                                                                               24      11070                                                                               4.5 × 10.sup.12                                                                270                                         21 5120 10180                                                                              4250                                                                               28      10680                                                                               5.8 × 10.sup.12                                                                640                                         22 5170 11410                                                                              4260                                                                               24      11430                                                                               6.4 × 10.sup.12                                                                830                                         23 5180 12300                                                                              4280                                                                               23      12310                                                                               7.2 × 10.sup.12                                                                890                                         24 5200 12310                                                                              4290                                                                               22      12320                                                                               7.5 × 10.sup.12                                                                950                                         25 5110 10190                                                                              4260                                                                               27      10250                                                                               4.7 × 10.sup.12                                                                740                                         26 5160 11430                                                                              4270                                                                               24      11450                                                                               6.1 ×  10.sup.12                                                               820                                         27 5190 12290                                                                              4290                                                                               23      12310                                                                               7.3 × 10.sup.12                                                                1010                                        28 5210 12320                                                                              4300                                                                               22      12330                                                                               7.6 × 10.sup.12                                                                940                                         29*                                                                               3580  7860                                                                              4230                                                                               34       8890                                                                               4.5 × 10.sup.12                                                                230                                         30*                                                                               5130 10330                                                                              4140                                                                               28      10820                                                                               5.1 × 10.sup.12                                                                280                                         31*                                                                               5170 11320                                                                              4290                                                                               24      11340                                                                               5.4 × 10.sup.12                                                                240                                         32*                                                                               5180 11650                                                                              4320                                                                               22      11670                                                                               5.8 × 10.sup.12                                                                290                                         __________________________________________________________________________      Note                                                                           Those marked with * are not included in the scope of this invention.     

                                      TABLE 3                                      __________________________________________________________________________     Ratio of main components          sintering                                    Pb(Mg 1/2   Pb(Ni 1/3     materials                                                                              temperature                                  No. W 1/2)O.sub.3                                                                          Nb 2/3)O.sub.3                                                                        PbTiO.sub.3                                                                           used    (°C.)                                 __________________________________________________________________________     33* 0.30    0.35   0.35   PbO      975                                         34* 0.30    0.35   0.35   MgO     1000                                         35* 0.30    0.35   0.35   WO.sub.3                                                                               1025                                         36* 0.30    0.35   0.35   NiO     1050                                                                   Nb.sub.2 O.sub.5                                                               TiO.sub.2                                            37  0.30    0.35   0.35   PbO      975                                         38  0.30    0.35   0.35   TiO.sub.2                                                                              1000                                         39  0.30    0.35   0.35   MgWO.sub.4                                                                             1025                                         40  0.30    0.35   0.35   TiO.sub.2                                                                              1050                                         41* 0.30    0.35   0.35   PbO      975                                         42* 0.30    0.35   0.35   MgO     1000                                         43* 0.30    0.35   0.35   MgNb.sub.2 O.sub.6                                                                     1025                                         44* 0.30    0.35   0.35   TiO.sub.2                                                                              1050                                         45  0.30    0.35   0.35   PbO      975                                         46  0.30    0.35   0.35   MgWO.sub.4                                                                             1000                                         47  0.30    0.35   0.35   MgNb.sub.2 O.sub.6                                                                     1025                                         48  0.30    0.35   0.35   TiO.sub.2                                                                              1050                                         __________________________________________________________________________                     temperature        breakdown                                                   with the           voltage of                                  dielectric      maximum maximum                                                                             resistivity                                                                          laminated                                   constant        dielectric                                                                             dielectric                                                                          (20° C.                                                                       ceramic                                     No.                                                                               -55° C.                                                                      20° C.                                                                      125° C.                                                                     constant (°C.)                                                                  constant                                                                            n · cm)                                                                     capacitor (V)                               __________________________________________________________________________     33*                                                                               2550  6670                                                                              7080                                                                               60       8230                                                                               3.7 × 10.sup.12                                                                170                                         34*                                                                               3730  9370                                                                              7350                                                                               52      11310                                                                               4.2 × 10.sup.12                                                                210                                         35*                                                                               4370 10130                                                                              7130                                                                               46      11510                                                                               5.3 × 10.sup.12                                                                230                                         36*                                                                               4850 10920                                                                              7280                                                                               42      12130                                                                               6.1 × 10.sup.12                                                                220                                         37 4510 10370                                                                              7210                                                                               45      11720                                                                               7.3 × 10.sup.12                                                                960                                         38 5070 11330                                                                              7450                                                                               43      12520                                                                               8.1 × 10.sup.12                                                                1080                                        39 5360 12070                                                                              7240                                                                               42      13410                                                                               8.3 × 10.sup.12                                                                990                                         40 5440 12150                                                                              7970                                                                               41      13430                                                                               9.1 × 10.sup.12                                                                1140                                        41*                                                                               3620  8460                                                                              6040                                                                               57       9670                                                                               5.9 × 10.sup.12                                                                210                                         42*                                                                               4240 10140                                                                              7550                                                                               50      11790                                                                               7.3 × 10.sup.12                                                                300                                         43*                                                                               4730 10960                                                                              7720                                                                               46      12310                                                                               9.1 × 10.sup.12                                                                280                                         44*                                                                               5090 11460                                                                              7630                                                                               42      12450                                                                               9.4 × 10.sup.12                                                                330                                         45 4360  9960                                                                              6820                                                                               44      11190                                                                               5.6 × 10.sup.12                                                                890                                         46 4940 11130                                                                              7420                                                                               42      12370                                                                               7.0 × 10.sup.12                                                                1090                                        47 5410 12090                                                                              7950                                                                               41      13360                                                                               7.1 × 10.sup.12                                                                1010                                        48 5420 13000                                                                              7960                                                                               41      13370                                                                               7.4 × 10.sup.12                                                                990                                         __________________________________________________________________________      Note                                                                           Those marked with * are not included in the scope of this invention.     

As is obvious from the results shown in Tables 1 through 3, the samples obtained by this invention method which is characterized in that magnesium tungstate powder (MgWO₄) is used as a starting material in the manufacture of the lead-based perovskite structure dielectric comprising lead magnesium tungstate [Pb(Mg_(1/2) W_(1/2))O₃ ] showed superior characteristics. More specifically, compared to the samples obtained by the prior art method in which magnesium oxide (MgO) and tungsten oxide (WO₃) powders were mixed, calcined and wet pulverized with other metal oxides, the present invention samples have a higher dielectric constant, more stable temperature characteristic of the dielectric constant in respect of sintering temperatures, a higher resistivity, and multilayer, capacitors manufactured with this powder also have a higher breakdown voltage.

The method of this invention can obviate such problems as occurrence of a liquid phase between lead oxide and tungsten oxide as well as deterioration of characteristics caused by weak reaction of magnesium oxide. All the lead-based perovskite structure dielectrics containing lead magnesium tungstate as a main component can achieve the same effect. Similar effect can be attained by using compounds of which lead is partly substituted with barium, strontium or calcium. Similar effects are obtained in ceramic compositions containing as an additive a small amount of manganese oxide (MnO₂), lead manganese niobate [Pb(Mn_(1/3) Nb_(2/3))O₃ ], lead manganese tungstate [Pb(Mn_(1/2) W_(1/2))O₃ ], niobium oxide (Nb₂ O₅), etc.

As shown in Table 2 under the numbers 25˜28 and in Table 3 under the numbers 45˜48, similar effects were obtained by the method using additionally the powder of nickel niobate (NiNb₂ O₆) or magnesium niobate (MgNb₂ O₆) which are synthesized in advance.

The effect similar to the above was obtained when a combination of powders of magnesium hydroxide Mg(OH)₂ and tungsten oxide (WO₃) was used by wet-mixing as the material for synthesizing magnesium tungstate (MgWO₄).

In addition to the composition groups mentioned above in the preferred embodiments, this invention achieved the same effect in the manufacture of ceramic compositions containing as main components one or more perovskite compounds such as lead magnesium niobate [Pb(Mg_(1/3) Nb_(2/3))O₃ ], lead nickel niobate [Pb(Ni_(1/3) Nb_(2/3))O₃ ], lead zinc niobate [Pb(Zn_(1/3) Nb_(2/3))O₃ ], lead iron niobate [Pb(Fe_(1/2) Nb_(1/2))O₃ ], lead manganese niobate [Pb(Mn_(1/2) Nb_(1/3))O₃ ], lead titanate (PbTiO₃), lead zirconate (PbZrO₃) and lead magnesium tungstate [Pb(Mg_(1/2) W_(1/2))O₃ ].

The ceramic composition obtained by this invention method is quite suitable as a dielectric ceramic composition to realize multilayer ceramic capacitors which have high dielectric constant, stable temperature-characteristics of dielectric constant, high resistivity, large capacity per unit volume, small temperature characteristics of capacity, and high in breakdown voltage. 

What is claimed is:
 1. A manufacturing method for dielectric ceramic compositions including steps of synthesizing, in advance, a powder of magnesium tungstate (MgWO₄) as raw material for magnesium (Mg) and tungsten(W) in a dielectric ceramic composition of lead-based perovskite materials composed of 30 to 98% lead magnesium tungstate (pb(Mg_(1/2) W_(1/2))O3), mixing the powder of magnesium tungstate (MgWO₄) with powders of lead oxide (PbO) and at least one other metal oxide constituting component elements of the dielectric ceramic composition of lead-based perovskite material, and sintering the mixture of powders of the magnesium tungstate, the lead oxide, and the at least one other metal oxide at a temperature of 900° C. to 1050° C. to provide a dielectric ceramic composition possessing a high dielectric constant, a stable temperature variation ratio, a high insulating resistance, and a high breakdown voltage.
 2. The manufacturing method for dielectric ceramic compositions as claimed in claim 1 wherein the powder of magnesium tungstate is obtained by the step of wet-mixing magnesium hydroxide (Mg(OH)₂) and tungsten oxide (WO₃).
 3. The manufacturing method for dielectric ceramic compositions as claimed in claim 1 wherein the at least one other metal oxide contains titanium oxide (TiO₂).
 4. The manufacturing method for dielectric ceramic compositions as claimed in claim 3 wherein the at least one other metal oxide further contains niobium oxide (Nb₂ O₅).
 5. A manufacturing method for dielectric ceramic compositions including steps of;a) synthesizing a powder of magnesium tungstate from oxides or hydroxides of magnesium and tungsten, b) mixing the magnesium tungstate powder with lead oxide powder to obtain a lead magnesium tungstate component, c) combining with the lead magnesium tungstate component, an oxide component including a metal selected from the group consisting of lead, nickel, niobium, and titanium, d) forming a lead-based perovskite containing 30 to 98% of the lead magnesium tungstate component and 2 to 45% of the oxide component, and e) sintering mixture of powders of the lead magnesium tungstate component and the metal oxide component at a temperature of 900° C. to 1050° C. to obtain a dielectric ceramic composition exhibiting a high dielectric constant, stable temperature variation ratio, a high insulating resistivity, and high breakdown voltage.
 6. A manufacturing method for dielectric ceramic compositions including steps of mixing powders of magnesium tungstate (MgWO₄), lead oxide (PbO), and titanium oxide (TiO₂), the amount of each of the powders being determined to compose 30 to 98 percent lead magnesium tungstate (Pb(Mg_(1/2) W_(1/2))O₃) and 2 to 45 percent lead titanate (PbTiO₃), and of sintering mixture of all of the powders at a temperature of 900° C. to 1050° C.
 7. A manufacturing method for dielectric ceramic compositions as claimed in claim 6 wherein the powders further include 30 to 35 percent niobium oxide (Nb₂ O₅) to form lead nickel niobate (Pb(Ni_(1/3) Nb_(2/3))O₃). 